The present invention relates to dispensers for sheet material, and in particular to paper towel roll dispensing cabinets having improved roll transfer mechanisms which sequentially dispense paper from first and second rolls thereof.
Dispensing cabinets have been designed to dispense two rolls of sheet material sequentially, so that upon depletion of the material from one of the rolls, the unwinding of the other roll is commenced. Some such dispensers involve a modification of the sheet material itself, such as an aperture formed in the material near the tail end thereof. The modification to the material is detected as the material on the roll nears or reaches exhaustion, and the mechanism accomplishing detection then operates some transfer means for commencing the dispensing of sheet material from the second roll.
Sheet materials are normally manufactured in a standard form so that they can be dispensed from any one of various types of cabinets. However, the cabinets as described inherently prevent the dispensing of such normal or unmodified rolls of sheet material, and the rolls must first be modified, at increased cost, to accommodate the detecting mechanism of the cabinet.
To avoid the additional cost of modifying the rolls of material, some recent dispensers use unmodified rolls and detect the tension of the material between the first roll thereof and a feed mechanism for delivering the material from the cabinet, and effect a transfer of material from the second roll to the feed mechanism upon a loss in the tension of the material from the first roll. Ideally, the tension of the first roll material is lost only when the tail end of the material leaves the core of the roll upon depletion of the roll. Unfortunately, however, in the normal use of such cabinets the tension is occasionally lost, at least momentarily, due to causes other than depletion of the roll. For example, a bind occurring in the rotation of the roll may, upon being overcome, cause the roll to jump and provide slack, or release the tension, in the material between the roll and the feed mechanism. As the cabinet cannot distinguish the particular cause of the tension loss, this may result in a "false" transfer of material from the second roll to the feed mechanism, which ordinarily either jams the mechanism, whereupon no material is delivered from the cabinet, or causes the mechanism to simultaneously deliver material from both of the rolls, which wastes and rapidly exhausts the entire supply of material.